Method of inoculating molten cast iron



United States Patent 3,310,397 METHOD OF IN OCULATING MOLTEN CAST IRON Andrei Andreevich Gorshkov and Mikhail Vasiljevich Voloshchenko, Kiev, U.S.S.R., assignors to Institute Liteinogo Proisvodstva No Drawing. Filed July 18, 1963, Ser. No. 296,119 2 Claims. (Cl. 75-130) The invention relates to the methods of inoculating molten cast type iron with chemical reagents.

The problem concerning treatment of cast type iron by forming in it a spheroidal graphite of globular shape without any further heat treatment, by inoculating it with chemical reagents, for instance, with silicocalcium has not yet been solved satisfactorily.

It is will known that castings should be subject to heat treatment (malleablizing) in an oxidizing or neutral atmosphere in order to form a spheroidal graphite in malleable cast iron. At the same time, the carbon present in the cast iron in the form of cementite is converted into graphite having the shape of round particles. However, the application of this method of heat treatment of cast iron complicates its process of manufacture.

In order to eliminate various drawbacks it is advisable to add naphthalene to the molten cast iron with the subsequent removal of primary and eutectic carbides by adding silicocalcium to the cast iron melt thus forming spheroidal graphite in the therebyproduced malleable cast iron.

One of the aims of this invention is to improve the processing of cast iron manufacture by reducing its treatment cycle.

Naphthalene can be added to the molten cast iron by various methods. For example, during experimental checking of the proposed method naphthalene was injected into the molten cast iron by means of steel tubes provided with openings.

The amount of added naphthalene is 0.1-0.3 percent of the weight of the molten cast iron. The solid naphthalene is gasified under the conditions of molten cast iron, which facilitates the formation of spheroidal graphite particles 3,310,397 Patented Mar. 21, 1967 in the cast iron castings. Then 0.3-0.6 percent by weight of silicocalcium is added, also contributing to the formation of spheroidal graphite by eliminating primary and eutectic carbides in the castings of malleable cast iron. The amount of silicocalcium being added depends on the thickness of the casting walls. The thinner are the walls, the more silicocalcium is added.

Test results show that the castings made of malleable cast iron without further heat treatment by adding the said amount of naphthalene to the molten iron acquire the following mechanical properties:

Tensile strength in kg./cm.'-=5565 kg. per sq. cm.

Relative elongation=1.03.0 percent Although the given invention has been described in conformity with the preferable method of realization, it is self evident that modifications and variations may be introduced without diverging from the idea and the scope .of this invention. Such modifications and variations are considered to be within the scope of the invention and the claims enclosed.

What we claim is:

1. A method for producing spheroidal graphite in cast iron comprising adding 0.1-0.3 percent naphthalene to molten cast iron.

2. A method for producing spheroidal graphite in cast iron comprising adding 0.1-0.3 percent naphthalene to molten cast iron and t-hen adding 0.3-0.6 percent of silicocalcium whereby the primary and eutectic carbides are eliminated as a result of the decomposition of the naphthalene.

References Cited by the Examiner UNITED STATES PATENTS 1,790,552 1/1931 Meehan -130 2,863,755 12/1958 Kurzinski 75-130 X 3,155,498 11/1964 Jandras 75-130 DAVID L. RECK, Primary Examiner.

H. W. TARRING, Assistant Examiner. 

1. A METHOD FOR PRODUCING SPHEROIDAL GRAPHITE IN CAST IRON COMPRISING ADDING 0.1-0.3 PERCENT NAPHTHALENE TO MOLTEN CAST IRON. 